To the Editor.
—Measurement of epithelial thickness and accurate location of corneal pathologic conditions have relied on slit-lamp examination and optical pachymetry.1 Recent advances in ultrasound transducer technology have enabled ultrasound pulses of shorter duration and higher frequency (10 to 100 MHz) to be produced. High-frequency ultrasound has been used to study the angle of the anterior chamber, but the resolution is sufficient to suggest a role for ultrasound in analysis of corneal diseases.2We used a high-frequency ultrasound scanning system that acquires serial parallel scans through a water-bath coupling medium.3 The ultrasound data were digitized and computationally enhanced to provide optimal estimates of interface locations using digital signal-processing techniques (the deconvolved analytic signal magnitude [DAS] of the echo data).3 This provided improved precision vis-à-vis conventional analog peak detection (A-scan).4A normal human corneal scan (Fig 1, top) shows the epithelial-stromal acoustic interface superficially at
Reinstein DZ, Silverman RH, Trokel SL, Allemann N, Coleman DJ. High-Frequency Ultrasound Digital Signal Processing for Biometry of the Cornea in Planning Phototherapeutic Keratectomy. Arch Ophthalmol. 1993;111(4):430-431. doi:10.1001/archopht.1993.01090040020013